Meanwhile, others wonder -- with the tram running, streetcar and light rail expanding, and more than 6 percent of the population already getting around by bicycle daily -- whether the city really needs another commuting alternative of this scale.

So, what does the proposal have going for it?

Besides the support of the Bureau of Transportation and Mayor Sam Adams, there’s the rapid popularity of bike sharing in other U.S. cities.

Streetfilms recently posted a video showing how Minneapolis’ Nice Ride program is gaining some amazing momentum after just a year on the streets. The program started last year with 65 stations and 700 bikes. Now, they're up to 116 stations and 1,200 bikes. "You've got to go big or go home," Minneapolis Mayor R.T. Rybak told Grist.

Meanwhile, in Washington D.C., the Capital Bikeshare program is having a hard time keeping up with demand. It will grow to 142 stations and 1,365 bicycles this fall.

The story is the same for networks in Louisville, Miami and Denver. Meanwhile, at least a dozen other U.S. cities are getting in line to launch their own bike-sharing networks. China is also preparing to launch the globe's most ambitious network in urban areas.

In Portland, alternative-transportation activist Chris Smith said he is supporting the idea, even though it has pitted him against some of his usual allies. “In other cities, it has proven transformative,” Smith wrote on his blog Tuesday. “From Paris to London to Washington D.C. adoption is very strong and changes people's travel patterns.”

Smith said there is even evidence that riding a bike-share bicycle is safer than riding your own bicycle.

In Britian, a new study says bike sharing “saves lives” by cutting down on traffic and pollution, and promoting exercise, among other things. “The doctors found that while the risk of road traffic injury and air pollution exposure rose fractionally among Bicing users, it was far offset by the improvement in health among members of the scheme - saving some 12 lives every year,” the UK Independent reported recently.

Portland transportation officials say they expect bike-share users to put at least 500,000 miles on the bikes in the first year. The Bicycle Transportation Alliance has pushed the idea as a crucial step toward 20-minute neighborhoods, where every resident can easily walk or bicycle to meet all basic daily, non-work needs within that time.

Of course, as some readers have mentioned, is it fair to measure the need for bike sharing compact downtown Portland -- where you can walk to many destinations faster than Portland Streetcar can get you there -- to that of a sprawling metropolitan such as D.C..?

Wrote “CityofMisfitToys” on OregonLive: “D.C. is 68 sqaure (sic) miles in size, Portland 150. Each city has a population roughly similar, DC 600,000 - PDX 584,000. Their metro areas are not even close, a 5.6 million for DC and 2.3 for PDX.”